“We could use him in the city to help us with our real estate,” Bloomberg sighed at a press conference. “He’s a city employee, after all. He’s getting paid.”

Rosenfeld, a lawyer and real-estate broker, collects a $100,049-a-year salary, benefits and a growing pension — all while sitting in a DOE administrative office because he was caught allegedly ogling eight-grade girls’ rear ends at Queens’ IS 347 back in 2001.

He spends his day developing his $10 million portfolio, which includes properties in Queens, Great Neck, LI, and Florida. Now and then, he’s asked to make copies of papers for the office.

In 2001, the DOE failed to produce enough witnesses for an administrative hearing, so Rosenfeld was just docked a week’s pay.

But the department considered him too big a risk to be sent back into a classroom, so it exiled him to its infamous rubber room.

Each year, his pension — worth $85,400 a year if he were to retire today — grows by another $1,700.

“The process to remove somebody from the payroll, totally separate from the process to remove him from the classroom, these processes over the years either were created poorly or just evolved into that,” Bloomberg said.

“If you talk to a principal, a lot of them say, ‘I’m not even going to try to get rid of the teacher or remove him from the classroom, because I’ll spend all my time running back and forth and it’s going to take years.’ ”

The city is in tough negotiations with the teachers union over changes to the teacher-evaluation system that would make it easier to ID or fire bad apples.

“We want to figure out which [ones] need remedial help and give them the help, because we have a big investment in them,” Bloomberg said. “But if they can’t make the grade, remove them.

“. . . Then there’s the money issue.”

Without reform, the state could lose more than $1 billion in federal Race to the Top grants and other funds linked to the adoption of an effective evaluation system.

A statewide system signed into law in 2010 and approved by the state Board of Regents last year crumbled this winter, as school districts and unions failed to round out certain details.

Talks with the United Federal of Teachers recently resumed after breaking down last month.